Do I need to register an app before connecting?

Basically yes.

Whenever you want to use our APIs in order to go to production you need to first build and test your app in the sandbox, then emulate enough of a usage pattern that approximates your production level usage and allow us to monitor your app, then you would request a production key from us.

Could you tell us more about what exactly you are trying to do from Salesforce?

Makes sense.  thanks.

Yes - it looks like the only SMS function is from the softphone.  I am going to want to send SMS's from a Salesforce Contact record.  I thought that I would just build an embedded visualforce page in Salesforce, and call the SMS API's to my RingCental account.  Just working through the oAuth connection code now.

Good our developer portal has all the tutorials and documentation you need to develop your own integration originating from Salesforce.

If you need individual technical support I suggest that you search within the community first then post another detailed question or open a support ticket here